EP0117968B1 - Method of electroforming thin ceramic or refractory articles with various shapes or forms - Google Patents

Description

The present invention relates to a method for producing individual ceramic tiles or integrated in a set of thin ceramic tiles without mold or subsequent stamping of a ribbon of dough, this stamping always leading to a loss estimated at around 10%. These tiles are made raw, with rectilinear contours or various cuts with spontaneously rounded edges. They can be made flat or have profiles in space. Their surface can be smooth, reguous or with a slight relief print. In addition, the technique makes it possible to incorporate texts, drawings or photographs with even very fine details, this in relief (or in hollow), these patterns being really embedded in the ceramic tiles; it may also involve the manufacture of substrates for electronics and electrical engineering. These are truly new performances vis-à-vis previous processes.

In Belgian patent no. 873 378 by the same author, an electrochemical process has been described which allows both the casting, molding, profiling, machining and surface treatment of parts from raw materials in the form of charged suspensoids and giving rise to conductive electro-deposits by rigorously controlled electrode reaction.

Furthermore in Belgian patent no. 880 933 also by the same author, are described complementary implementations of the technique of electro-deposition of ceramisable, vitrifiable, sinterable or polymerizable materials on metal supports or molds, as well as with the use of ion exchangers as an electrochemical casting surface and in particular for its particular application in the manufacture of flat glass.

Before detailing these new original principles, it should be recalled that the conventional techniques of ceramic manufacturing leading to similar products mainly use the techniques of pressing, stretching, casting between two plasters.

Pressing requires the very expensive manufacture of molds made of very special and expensive metals, allowing little diversification of shapes and models, the price of these molds requiring the production of large series of repetitive models. In addition, it is practically impossible to produce by this technique thin tiles (for example from 3 to 5 mm thick) of large formats such as 60x60 cm for example. The production of rounded edges requires special machining of the molds.

Flat drawing is used, but it requires subsequent stamping to shape without the possibility of rounding the edges; in addition, large thin formats are not very achievable by this second technique.

Plaster mold casting (between two walls) cannot be used for tiles; for large, thin formats, filling the molds with the slip presents problems and, moreover, very heavy plaster molds are fragile and require controlled drying after casting.

For electrical engineering applications, the electronic substrates are produced by the technique known as "Doctor blade" allowing the manufacture of thin alumina supports; but this technique is not adaptable to the manufacture of elements shaped individually.

Finally, if pressing allows a pattern to be printed in the tiles, the price of making molds becomes more and more prohibitive if we are dealing with complicated, varied patterns and very fine details. The raw materials used for pressing are also ill-suited for the reproduction of such patterns.

By stretching, this direct impression of patterns is really impractical. With plaster molds, pouring the plates with very fine decoration patterns is very delicate, the manufacture of the molds themselves presenting problems.

Finally, the transposition of drawings, texts or photographs on ceramics is conventionally carried out by techniques of sticking decals or by coating a photosensitive gelatin on biscuit. These processes do not really create an inlay of the patterns and for the photographs, it is only a plating produced with ceramic inks.

As for the technique of manufacturing soft paste ceramic by electrophoresis with the "double deposit" system, the machines described in the corresponding patent literature only produce a ribbon of paste to be stamped later without conditioning of edges, or relief, or incorporation of decoration patterns.

The present invention relates to an electrochemical process for producing individual ceramic tiles or integrated into a set of ceramic tiles, without mold or subsequent stamping of a ribbon of dough, of thicknesses between 1 and 15 mm. and whose formats per individual element can fit into surfaces up to 1000x1000 mm., the sets of tiles being of the "mosaics", "stained glass" or "puzzles" type, a process comprising the electrodeposition of raw materials in slip on the anode of an electrolytic cell and in which or uses a plurality of ion-exchange or semipermeable membranes or flat or profiled metal plates which are placed individually in the electrolytic cell in front of a cathode fixed, said membranes or plates being selectively masked using insulating paint or self-adhesive tape delimiting the contours of the tiles to be produced.

The present invention also relates to a device for implementing this method, as defined in claim 10.

The flat or profiled metal plates are preferably made of zinc, material galvanized, copper, iron, aluminum, brass, stainless steel, magnesium or nickel.

The outline of the tiles is drawn on these plates using a line of insulating paint or self-adhesive insulating tape whose width foreshadows the joints that will remain between the baked tiles when they are placed.

This technique therefore consists in carrying out selective masking of the anodes providing local electrical insulation and therefore a "reserve" where no deposition will take place during electrolysis. This selective masking can also be carried out on ion-exchange or semi-permeable membranes. The pieces of ceramic electrodeposited in non-insulated places develop up to the isolated contours. At the isolated limits, the electrodeposited material takes a spontaneous rounding in accordance with the distribution of the electric current lines at the borders between conductive and insulating zones.

It is possible, by the means conventionally used in electroplating, to exploit the edge effect either to achieve a slight extra thickness on the periphery of the tiles or to reduce this effect.

• à la figure 1a, un carreaux avec bord en surépaisseur;
• à la figure 1b, deux carreaux côte à côte sans effet de surépaisseur;
• à la figure 2a, une plaque préparée pour former de petits carreaux réguliers;
• à la figure 2b, une plaque préparée pour former des carreaux réguliers mais de plus grands formats qu'à la figure 2a;
• à la figure 2c, un ensemble de plaques préparées pour former un ensemble de carreaux réalisant un motif type "vitrail";
• à la figure 2d, une plaque préparée pour des carreaux type "puzzle" dont certains éléments présentent de réels emboîtements;
• à la figure 3a, un carreau galbé;
• à la figure 3b, un carreau en équerre;
• à la figure 3c, un carreau en cornière;
• aux figures 3d et 3d', des carreaux en coins;
• à la figure 3e, deux carreaux de claustra;
• à la figure 4, une vue schématique d'un dispositif de fabrication continue pour la mise en oeuvre selon la présente invention.

In order to better understand the invention, it is described by way of example and not limiting in relation to the drawings which represent:

• in Figure 1a, a tile with extra edge;
• in FIG. 1b, two tiles side by side with no thickening effect;
• in Figure 2a, a plate prepared to form small regular tiles;
• in FIG. 2b, a plate prepared to form regular tiles but of larger formats than in FIG. 2a;
• in FIG. 2c, a set of plates prepared to form a set of tiles carrying out a “stained glass” type pattern;
• in FIG. 2d, a plate prepared for “puzzle” type tiles, certain elements of which have real interlockings;
• in Figure 3a, a curved tile;
• in Figure 3b, a square square;
• in Figure 3c, an angle tile;
• in figures 3d and 3d ', corner tiles;
• in Figure 3e, two claustra tiles;
• in Figure 4, a schematic view of a continuous manufacturing device for the implementation according to the present invention.

In FIG. 1 a, where a tile (4) is shown with an extra thickness edge (3), the metal plate (1) is insulated in (2).

In 2b, these are two tiles (4a, 4b) formed side by side without any excess thickness, the metal plate (1) being insulated in (2).

Depending on the format of the plates, which can range, for example, from 10x10 cm up to 100x100 cm, it is possible to produce sets (Figures 2a to 2d) of tiles (4a, 4b, 4c, ...) with varied contours as shown in Figure 2a, where it is a plate (1) prepared to make small regular mosaic type tiles. In FIG. 2b, it is a plate used for tiles (4a, 4b, 4c, ...) with edges always straight but of larger formats. Individually, it is possible to produce 75x75 cm tiles from 1 to 5 mm thick for wall use. Thicknesses up to 15 mm are available for floor application.

In FIG. 2c, these are, by way of example only, of plates prepared for sets of tiles (4a, 4b, 4c, etc.) producing a “stained glass” type pattern whose shape and size of the elements can vary endlessly.

In FIG. 2d, the plate (1) is prepared for tiles (4a, 4b, 4c, etc.) of the "puzzle" type, certain elements of which have real interlockings.

It should be noted that these assemblies are manufactured in a single operation, this one requiring for example 3 minutes of electrolysis.

For the patterns having neither axis nor center of symmetry, the preparation of right and left models can prove to be interesting to develop the wall or floor patterns in two dimensions with possibility of connection of the joints between the various elements of the patterns.

The preparation of the plates (1) is carried out very easily and therefore makes it possible to make the technique very flexible and to vary the models at very little cost, since it is simply a matter of changing a design on the plates.

If insulating paint is used, this can be applied with a freehand brush or with a stencil or by the screen printing technique on the anode, the areas of the anode not covered. defining the shape of the manufactured tile (s), the isolated zones determining the empty spaces around, between the tiles or voids inside them. With adhesive tapes of well calibrated width, the same effect is obtained and it is therefore also possible to prepare plates very easily and very quickly.

The flat plates (1) being used to make flat tiles, it is possible to make structures in space by giving any shape to the plate either by stamping, bending, bending, welding. The technique in this case leads to the production of profiles with a thickness of 1 to 5 mm. and for example, certain achievable shapes such as curved tiles (figure 3a), square (figure 3b), angles (figure 3c), corners (figures 3d, 3d '), claustra (figure 3e), of straight tubes or bent, the contours of these structures being always delimited for the technique of selective masking of metal sheets or membranes using paint or insulating tape.

Tiles with rough surface more or less irregular imitating pumice or lava can be obtained on anodes made of metallic deposits projected hot by gun or plasma torch and by the technique of zinc plating with hot gun on metal support or made of plastic. For example, metallization on such a support with a molten zinc spray gun is very suitable for making anodes suitable for this type of tile with an irregular rough surface.

Ceramic "bas-reliefs" 3 to 10 mm thick can thus be produced on anodes formed from sheet metal repelled or hammered from the various metals mentioned above. Molded or stamped supports made of organic polymer materials metallized on the surface using a conductive paint (Zn, Cu, Ag, Ni) or metallization by chemical method (examples: copper, nickel, silver) allow reproduction by double molding (negative, positive) of existing bas-reliefs. Plates with relief obtained by electroforming or electro-machining in various metals are also useful for this production of bas-reliefs. These can be 3 to 10 mm thick.

The prior etching of the metal plates either mechanically or by acid attack (etching technique or photogravure on zinc, copper, magnesium plate) allows the transposition on the ceramic of very varied intaglio or relief patterns.

By photoengraving on a metal plate of zinc, copper or magnesium, it is the photoengraving plate itself which serves as an anode for manufacturing the tile. In these cases, it is of course the face of the tile against the anode which includes the etching.

We reproduce text as well as line drawings or photographs of landscapes, characters, paintings, etc. In these latter cases, the photos reproduced by photogravures undergo the "screening" operation with wefts of all kinds. species.

The photographs are reproduced on the ceramic with a relief corresponding to the engraving depth of the metal plates. Depending on the case, take the negative photos or slides for the exposure of the photoengraving plates.

The photographs are thus truly inlaid in relief in the ceramic, this with very fine details.

After firing, it is possible to reveal the photographs by inking with a roller with ordinary printing inks or with ceramic or colored enamel inks.

By screen printing, we can work with several inks or enamels of different colors and thus reproduce color photographs. You can also apply coloring oxides to the tiles after firing.

Important documents (reproduction of text or any work of art) can thus be kept in fire-resistant forms.

These reproductions can be made on flat or profiled tiles; it is sufficient to do this either to use the engraved plates as an electrode, or to incorporate the engraved plates into the electrodes of larger format to produce a set of ceramic elements of which all or some only will include the reproduction of a pattern.

Attenuated reliefs can be obtained on the tiles on the side opposite to that which is in contact with the metal. To do this, we use a property that the author discovered through the fundamental study of the mechanism of ceramic plating, that is to say that the nature of the metal and the form of the deposit of a thin layer of a metal d contribution to the support plate influences the speed of electroplating of the ceramic. It is therefore possible to exploit this property to obtain relief. It suffices in fact to carry out, according to a predetermined drawing, a metallic deposit at certain points of the electrode. If the metal supplied is of a nature to accelerate the speed of electrodeposition, at these locations a relief will appear on the external surface of the deposit. If the metal superimposed on the electrode is on the contrary of a nature to slow down the speed of electrodeposition, it will appear in correspondence with these places of the recesses on the external surface of the tile. For example, copper plating located on a zinc plate will produce hollows in the ceramic. Conversely, on copper plates, localized zinc deposits will cause raised areas. The couples Zn-AI, Cu-AI, Zn-AI as well as Fe-Zn can be used to produce these attenuated reliefs which have the very great advantage of being obtained on electrodes which remain practically flat. The metallic deposits in excess thickness on the plates are in effect under thicknesses remaining less than 1/10 th of a mm.

The metal plates are prepared by the usual techniques of electroplating after isolation of the parts of the base sheet which are not to be covered by a deposit of another metal.

These bi- or polymetallic plates can also be produced using a chemical deposit bath on a possibly non-metallic support.

With the help of flat tiles with various contours and profiled elements, with engraved patterns or not, it is possible to constitute "sets" of tiles adaptable to any form of kitchen tables, built-in sinks, window shelves, elements of integrated kitchens, bathroom accessories (handles for taps, doors, knobs, soap holders, etc.), feet for sinks, coverings for artistic living room tables.

The implementation of the present invention can be done in a continuous manufacturing device (Figure 4). This diagram corresponds more particularly to a device for the manufacture of large flat tiles. It can be easily adapted to the production of the other types of parts described in the present text, in particular for the production, in a single operation, of ceramic mosaic type panels, stained glass windows or puzzle with dimensions up to 1 × 1. m.

Surcettefigure4, there is shown in (5) the electrolysis cell whose dimensions can be, for example, 3 to 6 m in length, 15 to 20 cm in width and 1 m to 1.50 m height. In (6) is the entry and distribution of the feed slip; in (7) the evacuation of this slip which returns to the electrolysis tank.

The plates (1) serving as anodes are transported on a conveyor (8); at the entrance to the cell, they are energized thanks to the rail (9) and the sliding or rotating contact with which each plate is provided. The fixed counter electrode constantly immersed in the bath and serving as a cathode is located at (10). After electrodeposition, the charged plates are taken out of the cell and pass to the drainage and water washing station in (II).

In (13) the plates (1) loaded with the raw tiles (4), are placed on baking slabs (12) made of refractory material pushed on rollers first serving as a support for collecting the raw tiles which are then detached from the electrode plates after a time to adapt to each type of dough and the electrolysis conditions.

While the electrode plates are released following the conveyor, the released tiles and placed on the refractory tiles enter the fourtunnel roller (14) serving both for drying and for cooking. In (15) we recover the cooked tiles. In (16) the plates are cleaned and reconditioned before returning to the electrolysis cell.

The enameling not shown in Figure 4 can be incorporated into the production line. It can be done raw (before cooking) either by spraying with enamel slip or by the technique of the ink roller. In this case, it is the face of the tile on the electrode side which is most easily enamelled. With a sprayed enamel, it is possible to enamel the tiles with engraving in one color.

Double glazing on biscuit (therefore after passing through the baking oven) will be better indicated for glazing on the other side of the tiles or for multi-color glazing by the techniques described above in this application for patent or for the coloring and polychrome enameling of parts with various patterns in relief.

Since electrodeposition can take place in times of, for example, between 1 and 5 minutes for thicknesses of 1 to 5 mm, it is above all drying and firing which constitute the slow stage of the process for manufacturing the finished tiles.

If the capacity of the oven allows, it is possible with a cell of about 6 m in length, to make a plate of 1 mx 1 m per minute in a chain advancing at the speed of 1 m per minute. At this rate, a single cell could therefore supply the tile production line at the rate of approximately 50 m ² useful per hour or 1,200 m ² per 24 hours, which could lead to a production of 250,000 m ² per year. The chain would include around thirty plates, the renewal frequency of which depends on the reserve of useful metal. If it is zinc for example, it takes a consumption of about 400 µm in 24 hours of useful time (that is to say of immersion time). The reduction in the thickness of the zinc plates by approximately 400 J, lm would therefore be effected for the 30 plates of which only 5 are immersed at a time over a period of 6 × 24 hours.

During such a cycle of 6x24 hours = 144 hours, we would consume for the 30 plates (30 m ² ) and for the production of 6x1200 = ₇₂ 00 _M ² of tiles 5 mm thick (or about 90 tonnes of baked tiles) about 40 kg of zinc. The consumption of electrical energy strictly necessary for electroplating remains negligible; it is a maximum of 7 kWh per tonne produced. The voltages remain below 50 volts and the currents below 15 mA per cm ² .

It is certain that several electrolysis cells could be placed in parallel to increase production if necessary.

Claims (10)

1. An electrochemical process for making ceramic tiles, individually (4) or incorporated in ensembles of thin ceramic tiles (4a to 4d), without the use of a mould or further stamping of a paste strip, of between 1 to 15 mm thickness, whereby the sizes of each individual elements may be included in a surface of up to 1000x1000 mm, the said ensembles of tiles being of the type 'mosaic', 'lead-glass window' or 'puzzles', said process comprising electrodeposition of raw materials in the form of a slip, on the anode of an electrolysis cell or tank wherein there is used a plurality of ion-exchange. or semipermeable membranes or planar or contoured metallic plates which are moved individually in the electrolysis cell in front of a fixed cathode, said membranes or plates being selectively masked with isolating paints or adhesive tape delimiting the contours of the tiles to be produced.

2. A process in accordance with claim 1 wherein the planar or contoured metallic plates are made of zinc, galvanised materials, copper, iron, aluminium or nickel.

3. A process in accordance with claim 1, characterised by the fact that paint is applied with a stencil-plate and a brush or by silk screening on the anode and in which the uncovered regions of the anodes determine the form(s) of the tile(s) to be produced, the isolated parts defining the empty spaces around, between or inside said tiles.

4. A process in accordance with claims 1 and 2, characterised by the fact there are provided ceramic shaped pieces of 1 to 5 mm thickness comprising curved tiles, right angles tiles, corner tiles, elements of close to tiles, 'cloisters' elements, straight tubes or bent tubes on metallic embossed, curved, folded or welded sheet metals.

5. A process in accordance with claims 1 to 3 characterised by the fact there is obtained ceramic bas-reliefs of 3 to 10 mm thickness using anodes made of embossed or hammered metallic plates or galvanised embossed support of organic polymers or metal plates shaped by electroforming or electromachining.

6. A process in accordance with claim 1 to 3 characterised by the fact transposition on ceramic of hollow or relief motifs, engravings, drawings, texts, photographs is made after engraving the plates used as anodes, such engraving being made mechanically or by acid attack for example using the process of etching or photoengraving onto zinc, copper or magnesium plates.

7. A process in accordance with any one of the claims 1 to 3 or 5, for reproducing photographs possibly in colors, characterised by the fact there is applied color oxides, enamels or printing ink on the tiles after firing.

8. A process in accordance with any one of the claims 1 to 3 wherein there is obtained attenuated reliefs, characterised by the fact there is used bimetallic anodes, in particular Zn-Cu, Zn-Al, Zn-Fe, Cu-Al the relief being produced by the difference in ceramic electrodeposition velocities due to the nature of the metal or the form of the deposit of a thin layer of supplemental metal on the plate in accordance with the desired motif.

9. A process in accordance with any of the claims 1 to 3 wherein there is obtained tiles with a rough, irregular and unpolished surface characterised by the fact there are used anodes consisting of metallic deposits laid down with a spray gun or plasma torch and by the techniques of galvanising with a hot spray gun on a metallic or plastic support.

10. Apparatus for carrying out the process in accordance with claims 1 to 8, such apparatus comprising an electrolysis cell or tank (5), a conveyor (8) transporting plates (1) used as anodes into the electrolysis tank, a rail (9) for applying electric voltage to said plates, a drip tray (11) and a water spray station, a station (13) with refractory floor tiles (12) moving on rollers, a tunnel furnace (14) for drying and firing, a cleaning and reconditioning station (16) of plates (1), the electrolysis tank comprising a counter-electrode (10) used as cathode, an entry for distribution and an exit for the slip, said exit being placed in such a way as to return the slip into the electrolysis tank, the conveyor being such that plates are moved into the electrolysis tank, and that plates with the green tiles thereon (4) are transported to the dripping and water cleaning station, then towards station (13) wherein the tiles (4), laid on refractory floor tiles and detached from the plates (1) are transported into the tunnel furnace (14), the conveyor (8) moving then the plates (1) towards the cleaning and reconditioning station (16) before returning said plates towards the electrolysis tank.

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